An example of a food product that yields high levels of acid for the body to dispose of is a cola drink. Phosphoric acid is one of the ingredients listed on the cola container. The pH of cola is ~3.0, ranging from 2.8 to 3.2. The human kidney can excrete urine with a pH no lower than 5. If one ingests and fully absorbs a beverage with a pH of 3, one has to dilute it 100-fold to achieve a urinary pH of 5. Thus, a can containing 330 mL of cola would result in 33 L of urine! This does not happen because the body buffers the acid of the soft drink. For full buffering, 1 L of cola requires some four tablets of Tums, which contain 16 mEq of carbonate as the calcium salt.

A relevant comparison of the metabolic effects of acid phosphate and neutral phosphate was published by Lau et al. (1979). Young healthy adults consumed identical diets plus 2 g of phosphate, either acidic or neutral. The total phosphate ingested was identical, but the acid phosphate group ingested an excess of 24 mEq H+. Net urinary acid and calcium excretion were measured. Urinary calcium excretion per day was 52 mg greater in subjects consuming acid phosphate than in those ingesting neutral phosphate. Clearly, it is not how much phosphate is consumed that affects urinary calcium, but whether it is in a chemically neutral or acid form.

So, uh, I guess the phosphoric acid could have a leaching effect on bone calcium if you're not getting enough calcium and/or veggies in your diet. I don't really like that paper as a whole, but I'm too lazy to look up the papers it's citing.

The "rumor" was that Aspartame was rushed out to replace Saccharine and Aspartame was found to synthesize into Formadehyde and deposit in the brain causing brain lesions.

Don't know how much of this is true.

I've heard a few times that this happens when it warms to body temperature, which is why you should never leave a pallet of diet soda out in the sun. Never took the time to see if it was true, though. Bottom line is that, even without the sugar, the other ingredients in sodas are just bad for you in general. Colas in particular have been linked to kidney stones.

I actually gave up soda years ago. You'd be surprised how little I miss it.